Floating units in the context of the present document are, for example, ocean-going craft, such as ships or submarines, or else fuel-consuming offshore installations, such as drilling rigs or wind power plants. For the sake of simplicity, to represent these, ships are referred to hereafter.
Fuels for ships (often also designated, in this context, as “propellants” or “combustibles”) are distinguished by a high sulfur content of up to 5% by weight. Since shipping has increased greatly in recent years due to increasing international trade, its share of environmental pollution in harbors and inshore waters has risen markedly. Thus, in particular, the sulfur-containing exhaust gas constituents, such as SO2, are especially harmful. There has therefore, for some time, been efforts to limit the sulfur emissions by ships by limiting the sulfur content of the fuels. For the SECAS (SOx EMISSIONS CONTROLLED AREAS) of the North Sea and Baltic Sea, it is prescribed, for example, that only fuels with a maximum sulfur content of 1.5% by weight, and in harbors even only sulfur-free fuels (content <0.1% by weight), should be used. Similar regulations apply on the West coast of the USA. When traveling in these waters, ships are monitored as to whether only fuels with a content below the prescribed limit are currently being employed. There is a threat of severe penalties in the event of violations.
Furthermore, outside the statutory sea areas, fuel with any sulfur content is allowed to be burnt on the world's oceans. Since low-sulfur fuel is more costly than fuel with a high sulfur content, ships are operated with cheap sulfur-containing fuel over most of their trip and low-sulfur fuels are used only in specific areas. This means that, in future, ships will bunker fuels having different qualities.
EU Directive 2005/33/EC provides,                from 11 Aug. 2006, for the introduction of a sulfur limit value of 1.5% for ship's fuels which are used by ships in the Baltic Sea and, from 11 Aug. 2007, in the North Sea and in the English Channel, in order to reduce acidification and improve the air quality,        from 11 Aug. 2006, for the introduction of a sulfur limit value of 1.5% for ship's fuels which are used by passenger ships in a scheduled service from or to a Community harbor, so that the air quality is improved and, in order to ensure an EU-wide supply of low-sulfur ship's fuels, a sufficient demand is afforded,        for the introduction of a sulfur limit value of 0.1% from 1 Jan. 2010 for ship's fuels which are used by ships on the inland waterways and at berths for diesel engines, so that the air quality in harbors and on inland waterways is improved,        contrary to the above-described limit values for heavy oils, for issuing a permit to ships for the use of an approved emission-reducing technology, insofar as these ships constantly achieve at least equivalent emission reductions and it is documented in detail that all waste flows discharged to closed harbors and river mouths have no effect on the ecosystems,        for the proper management of logbooks with indications of the fuel changeover to become a condition for ships to be able to enter harbors of the EU Community,        for the sulfur content of all fuels sold in the sovereign area of the member states of the EU to have to be noted by the supplier on a delivery note accompanied by a sample,        for samples of ship's fuels to be taken and checked for their sulfur content.        
A serious problem is that the fuel quality is stipulated internationally in very different ways and not by generally valid laws or standards. In particular, it is to be expected, for example in harbors in Asia, South America or Africa, that the fuel is sold with false certificates, that is to say the sulfur content is usually higher than acknowledged in the certificate. Since, during controls in the areas of limited emissions, not only are the certificates inspected, but direct samples of the fuel are also taken and investigated, the ship's captain may be presented with considerable problems when too high a sulfur content is found (financial penalties, disposal of the false fuel, etc.).
The knowledge of the sulfur content of the fuel has not hitherto been necessary in order to operate a ship, since a limitation of the sulfur emissions for ships in specific sea areas has been implemented for only a very short time. The EU first decided in 2003 upon measures for limiting the sulfur content, the implementation of which is provided for in stages up to 2010.A lowering of the sulfur content to 1.5% by weight for the fuel of ocean-going ships (this applies to SECAS North Sea and Baltic Sea) is provided for 2007.
The sulfur content is at the present time usually measured only when the fuel is produced at the refinery. The ship's captain then has to trust in the correctness of the certificate, but without being able to check it himself.
From [Innov-X-Systems/Maersk Fluid Technology, “On-Board Elemental XRF Analysis of Oils & Additives”, 2006], an appliance, referred to as a “Sea-Mate™”, is known, which, for example, can be operated on a ship and can investigate samples of fuels with regard to their sulfur content. However, the sampling and subsequent analysis are complicated and time-consuming.